Build could be better, front lens rotates during focus, no full time manual focus.

I just bought this lens from a fellow FM'er and I am very pleased with it. I have owned and used the Tamron 75-300 and the Canon 75-300 III, also the Canon 70-200 F4 L w/ Canon 1.4II teleconverter and this lens has the best image quality of all three. I hated having to stop and add and remove the teleconverter for the 70-200, whose zoom range always seemed to short to me. It is light enough to carry around for hours without being uncomfortable and the new image stabilization rocks. I can take shots at 300mm with a shutter speed of 1/60 and get a sharp photo. I think Canon really hit the mark with this lens. This lens is designed for consumers ie. hobbyist who generally have the luxury of babying their equipment instead of the professional who uses his gear like a tool day in and day out. That being said the build quality is sufficient for a consumer, for a professional, invest in professsional grade lenses (L). This would also make a great travel lens for those who have the big heavy L zooms but want to travel lighter and not give up alot in the image quality department.

This is my first L lens and I have had it about 6 weeks now. I can only echo all of the positive statements about this lens. I have an excellent Tamron 28-75 F2.8 and while it is sharp, it doesn't produce the colors and contrast that this lens does. In my mind, that is one of the main things you are paying for when you buy an L lens. Using it with a Canon 1.4x teleconverter does little degrade the image. In fact, I have to check my exif data on some shots to be able to tell which ones I used the converter on and which ones I didn't. I give this lens a 10 for what it is. I can't penalise it for not being an F2.8 or faster, or not having IS. You know what this lens is when you buy it. I also can't penalise it for not having a tripod ring since in my opinion it just doesn't it. I use it on my 300D with teleconverter on a monopod and tripod with no problems. If your tripod droops when you put a camera and this lens on it then you need a better tripod head, not a tripod ring. Best thing is I paid $475 for it used and I know if my needs should change and I should want to sell it for a faster 2.8 version, I can get all of my money back.